Have you tried to change the background suppression feature? It may be worth a try.
My department has a Altallink C8030 fleet and we noticed the ones used in a high usage area eventullly gets the following print out issues.
Users when trying to use Outlook for calender printout has the background color text mixed in with the font/text, leaving a white out area as attached. This only occurs in this instance with the machine working fine otherwise.
The toner was replaced with new ones with the print calibration option ran.
Both times a tech was called to my site they claimed it was a user/driver issue.
Neither I the site's printer technican changed anything on the printer sever/driver side nor the end users changed any Outlook/printier settings when they print out thier sheets.
Printing the same document on another C8070 printer the printout comes out with no issues.
The tech just ends up vacuuming the interal parts and told "To gave it a few days" but the issue remains.
With this printer being in the head department, we switched out the model with another one until a few months later on the issues happpend on the switched machine too.
It is very disruptive to have to switch out the printers and now with my department downsizing we now have limited physical machince so this workaround will soon not be an option.
Any advice towards a more permament soulution will be valued.